When rotary lawn mowers began to replace conventional hand mowers they were relatively simple machines having a mower blade attached directly to the end of the crankshaft of a vertical shaft gasoline engine or other suitable power source mounted on the deck of the mower. However, for various reasons, the principal one being to minimize the safety hazards involved in the operation of walk-behind rotary lawn mowers, clutch/brake mechanisms have been proposed or developed to stop rotation of the mower blade while allowing the engine to continue running. The clutch/brake device is interposed between the mower blade and the crankshaft of the engine to selectively establish a torque transmitting connection between the blade and the crankshaft or stop rotation of the blade, both in response to operator control. Clutch/brake mechanism generally incorporate a control system for the operator to actuate from the usual operating station of the mower to select the clutch mode of the mechanism; the control also is adapted to select the brake mode of the mechanism when released by the operator. A large number of patents have issued disclosing various types of clutch/brake mechanisms, see e.g. U.S. Pat. Nos. 2,985,992; 3,247,654; 3,253,391; 3,837,450; 3,871,159; 4,044,533; 4,055,935; 4,122,652, 4,141,439; and 4,148,173.
We sought to achieve a number of important objectives with our new clutch/brake mechanism described herein. A principal goal of this invention was to develop a clutch/brake mechanism that would eliminate or greatly reduce the likelihood that its clutch and brake components would be engaged simultaneously. Another was to provide a mechanism in which such an objectionable consequence was rendered unlikely by making the clutch and brake functions each dependent upon shifting an axially movable element between one or the other of two axially spaced apart locations. Still another was to devise a clutch/brake mechanism that was of relatively simple construction and yet capable of combining quick and effective clutching and braking operations.